Chapter 4 - Acids and Redox

Question 1

What is an acid?

Answer 1

An acid releases [H]+ ions in an aqueous solution

Question 2

What is a strong acid?

Answer 2

An acid that completely dissociates in aqueous solution (releases all of its [H]+ ions into the solution)

e.g. HCl(aq) → [H]+(aq) + [Cl]-(aq)

Question 3

What is a weak acid?

Answer 3

An acid that partially dissociates in aqueous solution (releases a fraction of its [H]+ ions into the solution)

e.g. CH3COOH(aq) ⇌ [CH3COO]-(aq) + [H3O]+(aq)

Question 4

What is a base?

Answer 4

A base neutralises an acid to form a salt

Question 5

Examples of bases:

Answer 5

• Metal oxides (Na2O)
• Metal hydroxides (NaOH)
• Metal carbonates (Na2CO3)
• Alkalis (KOH)

Question 6

What is an alkali?

Answer 6

A soluble base in water, releasing [OH]- (hydroxide ions) into the solution.

Question 7

What is the general equation for a metal oxide/hydroxide reacted with an acid?

Answer 7

Metal oxide/Hydroxide + Acid → Salt + Water

Question 8

What is the general equation for an acid reacted with with an alkali?

Answer 8

Acid + Alkali → Salt + Water

Question 9

What happens when ammonia is reacted with an acid?

Answer 9

• NH3 + Acid → Ammonium Salt

• NH3 + [H]+ → [NH4]+

Question 10

What is the general equation for a metal carbonate reacted with an acid?

Answer 10

Metal carbonate + Acid → Salt + Water + Carbon dioxide

Question 11

What is a titration?

Answer 11

A technique used to accurately measure the volume of one solution that reacts exactly with another solution

Question 12

What can titrations be used for?

Answer 12

• Finding the concentration of a solution
• Testing purity
• Finding an unknown chemical

Question 13

What are concordant results?

Answer 13

Results within 0.10cm^3 of eachother

Question 14

How to prepare a standard solution of Na2CO3:

Answer 14

• Add a known mass of Na2CO3 into a beaker and dissolve it by stirring with distilled water
• Pour the solution into a volumetric flask (also rinse the beaker with distilled water and pour this into the volumetric flask)
• Make up the solution to the desired volume with distilled water (read from the bottom of the meniscus)
• Place a stopper on the flask and invert several times

Question 15

When can a mean titre be worked out?

Answer 15

When two or more concordant titres are obtained

Question 16

When is the (total) oxidation number zero?

Answer 16

• For elements
• For compounds

Question 17

What is the (total) oxidation number for ions and polyatomic ions? e.g. [Na]+ and [SO4]2-

Answer 17

• The (total) oxidation number matches the charge
• [Na]+ has an oxidation number of +1
• [SO4]2- has an oxidation number of -2

Question 18

What do roman numerals represent? e.g. in iron(II) and iron(III)?

Answer 18

• Iron(II) represents [Fe]2+ with an oxidation number of +2
• Iron(III) represents [Fe]3+ with oxidation number +3

Question 19

What is oxidation?

Answer 19

The loss of electrons (OIL rig)

Question 20

What is reduction?

Answer 20

The gain of electrons (oil RIG)

Question 21

What is oxidation in terms of the oxidation number?

Answer 21

An increase in oxidation number

Question 22

What is reduction in terms of the oxidation number?

Answer 22

A decrease in oxidation number

Question 23

What is the general equation for a metal reacted with an acid?

Answer 23

Metal + Acid → Salt + Hydrogen

Question 24

Hydrochloric Acid

Answer 24

HCl

Question 25

Sulfuric Acid

Answer 25

H2SO4

Question 26

Nitric Acid

Answer 26

HNO3

Question 27

Ethanoic Acid

Answer 27

CH3COOH

Question 28

Priority table for common oxidation numbers:

Answer 28